Origin and history of canon

"a rule or law," Middle English canoun, Old English canon "rule, law, or decree of the Church," from Old French canon or directly from Late Latin canon "Church law, a rule or doctrine enacted by ecclesiastical authority," in classical Latin, "measuring line, rule," from Greek kanōn "any straight rod or bar; rule; standard of excellence," which is perhaps from kanna "reed" (see cane (n.)), but Beekes favors Pre-Greek origin.

The Latin word was taken in Christian use for "decree of the Church." The general sense of "a rule or principle" is attested from late 14c.; that of "standard of judging" is by c. 1600.

It is attested from c. 1400 as "the Scriptures, the books of the Bible accepted by the Christian church," and also extended to secular books of admitted excellence or authoritative supremacy (such as the Trojan legends or Avicenna's Liber Canonis Medicinae). The meaning "catalogue of acknowledged saints" is from 1727.

The fandom sense of "material regarded as veritable" is attested by 1934, originally in reference to the Sherlock Holmes series. The musical use in reference to a kind of fugal composition is from 1590s. Related: Canonicity.

The secular canon, with the word meaning a catalog of approved authors, does not actually begin until the middle of the eighteenth century .... [Harold Bloom, "The Western Canon," 1994].

"clergyman living according to rules," c. 1200 (late 12c. as a surname), from Anglo-French canun, from Old North French canonie (Modern French chanoine), from Church Latin canonicus "clergyman living under a rule," noun use of Latin adjective canonicus "according to rule" (in ecclesiastical use, "pertaining to the rules or institutes of the church canonical"), from Greek kanonikos, from kanōn "rule" (see canon (n.1)).